The present invention relates to an electrode water circulation and processing system and a hooded radiator for a water rheostat for measuring or testing the output characteristics of a power supply such as an electricity generator and an inverter.
As shown in FIG. 1, a conventional water rheostat A created by the present inventor comprises a base electrode 1 shaped as a bottomed cylinder and containing a prescribed amount of electrode water W which is circulated through the electrode, a main electrode 5 shaped as a cylinder and vertically extending through an electrically insulating support 3 vertically extending through the center of the bottom 1a of the base electrode 1, and an electrically insulating cylinder 7 covering the main electrode and vertically slidable to adjust the length of the uncovered portion of the main electrode 5. A water drain hole 2 is provided in an appropriate portion of the bottom 1a of the base electrode 1. A power cable 4 for a power supply not shown in FIG. 1 is connected to the lower end of the main electrode 5, which is located outside the electrically insulating support 3. A water feed port 6 is provided in the upper portion of the electrically insulating cylinder 7 so that the cooled water W is fed through the port 6.
A plurality of such water rheostats A are provided though not all of them are shown in FIG. 1, so that the main electrodes 5 of the rheostats A are connected to the single or three phases of the power supply, and the base electrodes 1 of the rheostats A are connected to each other through a earth cable 8 and grounded. If the number of the phases of the power supply is three, the water rheostats A are Y-connected to each other. The water feed port 6 and the water drain hole 2 in each of the rheostats A communicate with an electrode water cooling and processing unit B shown in FIG. 1 and disclosed in the Japanese Patent Laid-open Nos. 123287/1987 and 124474/1987.
The electrode water cooling and processing unit B functions so that the warmed water W drained from the water rheostat A is cooled and sent again to the rheostat A. The unit B comprises a radiator 9, a spray pipe 10 for spraying water to the rear of the radiator 9, a fan 11 for blowing air from behind the spray pipe 10, a duct 12 by which the air blown to the radiator 9 by the fan 11 and flowing to the front of the radiator 9 is guided so that the air is dispersed upward, a recovered water tank 13 provided under the radiator 9 to recover the water sprayed from the spray pipe 10 to the radiator 9 and falling therefrom, and a storage tank 14 storing the electrode water W which is circulated through the water rheostat A and the radiator 9.
The cooling and processing unit B has a pure water filling passage line 20, an electrode water cooling and circulation passage line 22, a flushing return passage line 24, and a sprayed water feed passage line 27 among the radiator 9, the spray pipe 10, the recovered water tank 13 and the storage tank 14. The pure water filling passage line 20 functions so that the electrode water W in the storage tank 14 is pumped up by a pure water pump 16 through a water feed pipe 15 extending down into the storage tank 14 and is processed through filters 17 and 18 and a water purifier 19 which heightens the purity of the water. The electrode water cooling and circulation passage line 22 functions so that the electrode water W is received from the pure water filing passage line 20 to the feed portion 22a of the electrode water cooling and circulation passage line 22 and fed to the water rheostat A, and the warmed water drained from the rheostat A is sent to the lower inlet port 9a of the radiator 9 by an electrode water circulation pump 21 provided in the electrode water cooling and circulation passage line 22. The flushing return passage line 24 functions so that the electrode water W dividedly sent out from the drain portion 22b of the electrode water cooling and circulation passage line 22 upstream to the lower inlet port 9a of the radiator 9 is returned to the pure water filling passage line 20 by the pure water pump 16 while being cooled through a cooling coil 23. The sprayed water feed passage line 27 functions so that the water is pumped up, by a spray pump 25, through one of the water feed pipe 15 and a suction pipe 26 extending down into the recovered water tank 13 and is sent to the spray pipe 10. The cooling and processing unit B includes changeover valves 28, 29 and 30 connected to the passage lines 20, 22, 24 and 27.
A fan motor 31, speed controllers 32, 33 and 34 made of inverters to regulate the speeds of the fan motor 31, the pure water pump 16 and the spray pump 25, and a cooling coil 35 are provided further, as shown in FIG. 1.
Shown at C in FIG. 1 is an automatic control unit for vertically moving the electrically insulating cylinder 7. The automatic control unit C comprises a measuring instrument 36 which measures at least one of the electric power and electrical current supplied through the power cable 4 and sends out a measured value signal S1 corresponding to the electric power or the electrical current, a controller 37 which receives the signal S1 and sends out a control signal S2 resulting from the comparison of the signal S1 with a preset value, and an operating unit 38 which recieves the control signal S2 to move up the electrically insulating cylinder 7.
The water rheostats A, the electrode water cooling and processing unit B, the automatic control unit C and so forth can be installed on the cargo bed of an autotruck or the like so as to be rapidly conveyed. The storage tank 14 may be substituted by a pool.
The operation of the electrode water cooling and processing unit B is described in detail from now on. The purified water is sent to the feed portion 22a of the electrode water cooling and circulation passage line 22 through the water feed pipe 15 and the pure water filling passage line 20 and filled into the water rheostat A through the water feed port 6, as shown by full-line arrows in FIG. 1. At that time, the water is pumped up from the storage tank 14 by the pure water pump 16 so that the water flows through the pump 16 and the cooling coil 35 and is removed of sand and the like by the filter 17 and of chlorine by the filter 18 before the water enters into the water purifier 19. Although the electric conductivity of the water entering into the water purifier 19 is about 200 .mu.s/cm, the conductivity is decreased to about 1 .mu.s/cm by the purifier 19. If the electric conductivity of the water rises due to the dissolution of an impurity into the water as a result of the initial rotation of the electrode water pump 21, the water is drained and then subjected to the above-described processing and filling again. Since the maximum operating temperature of the water purifier 19 is 40.degree. C., the cooling coils 23 and 35 are used to keep the temperature of the water not higher than 40.degree. C. After the pure water filling passage line 20 is closed by the changeover valves 29 and 30, the electrode water circulation pump 21 is put into action so that the electrode water W is circulated through the electrode water cooling and circulation passage line 22, as shown by dotted-line arrows in FIG. 1. At the same time, the spray pump 25 is put into action so that the water in the storage tank 14 is pumped up through the water feed pipe 15 and fed to the spray pipe 10 through the sprayed water feed passage line 27 as shown by dotted-line arrows in FIG. 1, and is then sprayed from the spray pipe 10 to the radiator 9 as shown by dotted lines in FIG. 1. The fan motor 31 is also put into action to rotate the fan 11 to blow the air from behind the radiator 9, As the electrode water W flows through the water rheostat A, the water acts as an electric resistor so that it consumes electric power and is warmed thereby. The warmed water W is sent to the radiator 9 so that the water is cooled by the sprayed water while the warmed water flows through the radiator 9. The sprayed water is evaporated on the surface of the radiator 9 by the heat of the warmed water W flowing through the radiator, and is then sent out by the air blown from behind the radiator 9 by the fan 11, so that the evaporated water and the air are diffused upward along the guide plates 12a of the duct 12 in front of the radiator 9 as shown by dotted lines in FIG. 1. The electrode water W thus cooled by the radiator 9 flows out therefrom through the outlet port 9b thereof and is then fed again to the water rheostat A through the feed portion 22a of the electrode water cooling and circulation passage line 22. Some sprayed water, which is sprayed to the radiator 9 to cool the warmed water W therein but is not evaporated by the heat thereof, clings to the duct 12 and gravitationally falls therefrom so that the fallen water is recovered into the recovered water tank 13. When the water in the tank 13 has risen to the vicinity of the maximum level, the changeover valve 28 is switched so that the water is pumped up by the spray pump 25 through the suction pipe 26 and sent to the spray pipe 10. The recovered water tank 13 and the storage tank 14 may be connected to each other so as to dispense with the changeover valve 28 and the suction pipe 26.
If the electric conductivity of the electrode water W is to be decreased during the operation of the water rheostat A under a high voltage, the changeover valves 29 and 30 are switched so that the water shown by two-dot chain line arrows in FIG. 1 is circulated through the flushing return passage line 24, the pure water filling passage line 20 and the electrode water cooling and circulation passage line 22. At that time, the electrode water W is drained from the water rheostat A by the electrode water circulation pump 21, sent to the cooling coil 35 through the other cooling coil 23 by the pure water pump 16 and returned to the water rheostat A through the filters 17 and 18 and the water purifier 19, so that the water is removed of extraneous substances, chlorine and so forth, thus decreasing the electric conductivity of the water.
If the water rheostat A is to be put in operation at a heavy electrical current under a low voltage, a salt for electric conduction is dissolved in the electrode water W to make the electric conductivity thereof higher than that, 200 .mu.s/cm, of ordinary tape water, and the electrode water W is circulated through the rheostat A and the electrode water cooling and circulation passage line 22.
An electrode water temperature control unit D comprises a temperature measuring instrument 39, a temperature comparator 40, the speed controllers 32 and 34, the operating unit 38, an alarm 41, and a safety circuit breaker 42. The temperature measuring instrument 39 is provided at the lower inlet port 9a of the radiator 9 connected to the end of the drain portion 22b of the electrode water cooling and circulation passage line 22, and measures the temperature of the electrode water W flowing through the lower inlet port 9a, so that the instrument 39 sends out a measured values signal S3. The temperature comparator 40 receives the measured value signal S3, and sends out a control signal S4 resulting from the comparison of the measured value signal S3 with a preset value. If the control signal S4 has exceeded a preset allowable maximum temperature value, the comparator 40 sends out an emergency signal S5. The speed controllers 32 and 34 are made of the inverters to receive the control signal S4 to regulate the driving of the motor of the spray pump 25 and that of the motor 31 of the fan 11. When operating unit 38 has received the emergency signal S5, the unit 38 disengages a clutch not shown in FIG. 1. When the alarm 41 has received the emergency signal S5, the alarm makes a warning sound. At that time, the safety circuit breaker 42 provided in the half-way portion of the power cable 4 disconnects the power supply and the water rheostat A from each other.
The automatic control unit C and the electrode water temperature control unit D are included in a conventional electrode water circulation and processing system X for the water rheostat A so as to take safety measures against abnormalities.
If the electrode water circulation pump 21 has stopped or the driving capacity thereof has sharply fallen during the operation of the water rheostat A so that the flow rate of the electrode water W from the pump 21 has drastically decreased, the circulated quantity of the water becomes zero or reduced to result in a sharp rise in the temperature of the water in the base electrode 1 to boil the water into overflowing. This phenomenon is very dangerous. Since there is a lag time until the temperature measuring instrument 39 detects the sharp rise in the temperature of the electrode water W, arc discharge .alpha. occurs between the base electrode 1 and the main electrode 5 during the lag time. Until a short-circuit overcurrent due to the arc discharge is detected by the measuring instrument 36, the electrically insulating cylinder 7 is not moved down to completely cover the main electrode 5 to insulate it. For these reasons, moving down the cylinder 7 to insulate the main electrode 5 is likely to be too late to avoid a danger resulting from the occurrence of the arc .alpha..
Let us suppose now that vertical electrode plates P1 and P2 face each other in parallel in a fixed amount of water L in the water rheostat A', as shown in FIG. 2. When a voltage E applied to the electrode plates P1 and P2 is increased to a certain value, discharge takes place between them. If the electrode plates P1 and P2 were infinitely-extensive flat plates parallel with each other, the discharge would be most unlikely to take place between them. However, such infinitely-extensive flat plates do not exist in reality. The potential V on the surface of the electrode plate is expressed as follows: ##EQU1## In the equation, K, Q and r denote a coefficient, the amount of electric charge and the radius of curvature of the electrode plate, respectively. Since the electrode plate is flat, the radius r of curvature is infinitely large. However, the potential V on the corner .theta. of the electrode plate is equal to that in the case of r.apprxeq.O. The potential V in the case of r.apprxeq.O is infinitely high as understood from the above equation. Therefore, the discharge is most likely to take place on the corner of the electrode plate. The corner of each of the electrode plates can be eliminated by shaping the plate as a sphere or a cylinder. For such purpose, the main electrode 5 is composed of an upper and a lower hemispherical end portions 5a and 5b and an intermediate cylindrical portion 5c, as shown in FIG. 3. Since the radius of curvature of the base electrode 1 shaped as a bottomed cylinder and located outside the main electrode 5 is larger than that of the main electrode 5, the potential on the base electrode 1 is lower than that on the main electrode 5.
The discharge in the water W between the main electrode 5 and the base electrode 1 in the water rheostat A takes place due to a bubble generated by the local heating of the surface of the main electrode 5. When the bubble is generated between the electrodes 1 and 5, the area of the substantial mutual facing of the electrodes fluctuates. Since the movement of the bubble is irregular, the electric resistance between the electrodes 1 and 5 irregularly changes so that dielectric breakdown occurs. The only means for preventing and removing the bubble is cooling and cleaning the surface of the main electrode 5 with an uniform rapid flow of water.
A conventional water rheostat of such kind was invented by the present inventor and disclosed in Japanese patent application no. 251652/1987. After that, the form and constitution of the main electrode unit 43 of the water rheostat A was modified as shown in FIG. 4. FIG. 4 shows an electrically insulating support 3, a main electrode 5 on the support 3, an electrode connection rod 44, the bottom 1a of a base electrode 1 shaped as a bottomed cylinder, a fixed block 45 secured to the bottom 1a of a base electrode 1 by screws 46, and an annular seal 47 for preventing electrode water from leaking. The bottom 5a of the main electrode 5 is made flat in order to stably support the electrode 5 on the support 3. The bottom 5a is provided with a curved chamfer 5b at the periphery of the bottom 5a. Since the radius of curvature of the curved chamfer 5b is so small that when the temperature of the electrode water has risen to 65.degree. C., a bubble is generated on the curved chamfer 5b and arc discharge takes place at the bubble. For that reason, the maximum electric power applicable to the electrodes 1 and 5 is 650 kw. Because of the arc discharge, the electric power output across the electrodes 1 and 5 is likely to fluctuate so as to hinder proper measurement in a load test, reduce mechanical capacity and cause a burnout accident.
Since the conventional electrode water circulation and processing system X has only the radiator 9, the spray pipe 10, the fan 11 and the duct 2 for cooling the electrode water W, the cooling capacity of the system X is relatively low. However, if the radiator 9 is made larger in size to increase the cooling capacity of the system X, the radiator 9 occupies a larger space and the cost of equipment and running of the system X are augmented. For that reason, the output characteristics of the power supply cannot be measured at a heavy current under a high voltage with the use of the system X.